Kidney Function Tests

Kidney function tests are the tests performed to evaluate kidney functioning. These tests reveal the functioning and abnormalities, if any. Some of the commonly conducted laboratory tests are

BUN test – Blood, urea, and nitrogen

Creatinine – blood

Creatinine clearance

Creatinine urine

Blood urea nitrogen (BUN): TheBUN test measures the nitrogen content in blood urea. Urea is a waste product released from degradation of protein, which is filtered in the blood and excreted in urine by kidneys. The normal values of nitrogen in blood urea ranges from 7 to 20mg/dL. Elevated levels suggest impaired kidney function such as acute or chronic kidney disease, decreased blood flow to kidneys as in congestive heart failure and shock. Decreased concentration of BUN is not common and may occur in cases of malnutrition and severe kidney disease.

Blood Creatinine: This test measures the amount of creatinine in blood which signifies the filtering capability of kidneys. Creatinine is a byproduct of creatine produced when muscles are put to use. Creatinine is filtered from blood and excreted in urine by the kidneys. Normal value of creatinine is 0.8 – 1.4mg/dL Females have low creatinine than males because of the muscle mass. If the level of creatinine is more than the normal value it indicates kidney conditions such as glomerulonephritis, pyelonephritis, acute tubular necrosis, kidney stones, prostate disease, and complications of diabetes. Creatinine levels may be decreased slightly in pregnancy.

Creatinine clearance: This test determines the kidney functioning and suggests kidney dysfunction or decreased blood flow to kidneys as in congestive heart failure. Creatinine is the waste product released when the muscle is put to work. It is also done to estimate the glomerular filtration rate (GFR). The normal value in males is 97 to 137 mL/min and females is 88 to 128mL/min. If the GFR is high then it may indicate chances of kidney failure.

Urine creatinine: This test measures the amount of creatinine in urine. Creatinine is filtered by the kidneys and excreted in urine. The normal value of creatinine in urine is found 500 to 2000 mg/day and may vary with age. Any derangement in the values signifies the impaired kidney function.